stupid question????

[Bubba]

this may be a stupid quastion but i dunno...do they make fatty pipes for 4 strokes, because everytime i see them they are on a 2 stroke so i was onderin if its only a 2 stroke thing:confused:

[sparks400]

nope :D

[ride300exrider]

yea only 2 strokes can have fattys it has something to do with how the motor works i think, only being a 2 stroke

[Bender]

It's an expansion chamber in the exhaust pipe. 2 strokes need them to build power.

[stupid driver]

the expansion chambler creates a vaccume to suck out the exhaust. Unburnt fuel also gets into this expansion chamber. When the chamber gets thinner, waves of energy bounce off the sides and push the fuel back through the exhaust port into the cylinder. Hope this helps :confused2

[wilkin250r]

Just to add a little more detail to the explanations.

In a two-stroke, the piston does not push the gasses out. Instead, a pressure wave created inside the pipe helps to "pull" the exhaust gasses out, and then helps bring in the fresh fuel-air mixture. In a four-stroke, the piston pushes the exhaust gasses out as it travels upwards in the cylinder. The four stroke doesn't require the pressure wave created by the expansion chamber of the pipe.

Same principle applies to compression. In a two-stroke, both the intake and exhaust ports are open at the same time, so some of the fresh fuel-air mixture could possibly escape out the exhaust port. Another portion of the pressure wave created inside the pipe is timed exactly so that it will allow the exhaust out, and then hit the fresh fuel/air mixture, essentially stuffing it back into the cylinder, helping to build pressure and compression.

Obviously, in a four-stroke, the exhaust valves are closed when the fresh fuel-air mixture comes in, so there is no possibility of losing any out the exhaust port.

Basically, the expansion chamber of a two-stroke pipe has certain functions that it performs that are very necessary for efficient operation. A four-stroke doesn't need any of those functions, they are already performed by the valves.